1. Field of Invention
The present invention relates to a power supply that can be used with most needleless injectors or other drug delivery devices for transcutaneous delivery of drugs or other rapid drug delivery. The power supply has a working gas and no active seals that can provide a leak path for the working gas out of an enclosed volume.
2. Description of Prior Art
Needleless injectors are used to inject drugs of various types transcutaneously without using a needle which is the standard modality for drug delivery. Several components that generally form a needleless injector include a power supply, a drug reservoir, and a reset mechanism. The needleless injector is usually activated from a loaded to an unloaded state by some type of trigger mechanism and is held in a loaded state prior to activation by a latch mechanism. Typically the drugs used with most needleless injectors are in a liquid or suspension form although it is possible to inject dry powder or crystalline drug transcutaneously using some needleless injector designs. The drug is usually contained in a reservoir or ampule which can take on many forms. Most ampules have a piston-like mechanism that is associated with them to apply a force onto the contained drug and force the drug out of an orifice at a high velocity and typically through the cutaneous tissue of the patient's arm. Often the piston-like mechanism of the ampule interfaces with a piston or moving surface of a power supply that generates the energy and force needed to force the drug out of the ampule orifice. The orifice found in the ampule of some needleless injectors can be positioned in contact or adjacent to the patient's skin or it can be positioned a small distance away from the skin. Some needleless injectors have a built in ampule that is not removable and can be reused. This type of design may provide a lower overall cost of use but can require cleaning and sterilization by the patient on a regular basis. Other needleless injectors are made with a built in ampule that can be removed either between injections or after several injections for purposes of cleaning or filling the ampule. In this design only the ampule need be disassembled, cleaned, and sterilized on a regular basis. Still other needleless injectors have a place or compartment for a disposable ampule which can be a one-time-use ampule that is provided to the patient in a fully contained state. This design provides the patient with an easy to use, easy to maintain system but may be more costly to provide individually packaged disposable drug doses. Some drugs are not able to withstand individual packaging in a disposable ampule due to material considerations. Other drugs can require such individualized doses for each patient that prepackaging the drug in a separate ampule may be impractical. Some needleless injectors provide for a syringe type of ampule that can be filled by the patient in a manner similarly to a standard syringe. Several problems can arise from this type of ampule system including leakage and lack of control of dose volume. Needleless injectors have advantages over conventional needle injection due to their less invasive nature, the psychological advantage of not inserting a needle through the skin, and other potential advantages including less pain and better sterility control. The present invention is a power supply that can be used with almost all needleless injectors regardless of the type of drug reservoir or ampule they have and regardless of the type of drug reservoir they may interface with.
A needleless injector has a power supply that provides the energy to drive the drug out of the orifice of the ampule. Many different types of power supplies are used with needleless injectors. Mechanical springs including disk springs and coil springs can be compressed to store potential energy that is later released to drive a liquid or dry powder drug transcutaneously into a patients body without the use of a needle. Such springs can be modified to provide spring rates and spring constants that will provide a comfortable and effective delivery of the drug into the patients tissue. Other power supplies include compressed gas cylinders and pistons that compress a gas and store potential energy in the compressed gas; this energy is stored and returned to drive the drug with a high velocity through an orifice into the patient. An additional power supply for needleless injectors include a disposable carbon dioxide liquid-gas cylinder that converts a liquid carbon dioxide into a high pressure carbon dioxide gas that is used to supply the energy to drive the drug through an orifice at high velocity; disposable liquid-gas cylinder power supply systems other than the carbon dioxide power supply could also be used with a needleless injector. The present invention is a power supply that can be used to replace the power supplies of other needleless injector designs including mechanical springs, compressed gas, and disposable liquid-gas systems. Components from other needleless injector patent designs can interface with the power supply of the present invention to provide a more efficient needleless injector device.
The needleless injectors with spring and compressed gas power supplies are generally equipped with or interface with a reset mechanism to restore the power supply to its compressed state such that the needleless injector can be used again for another needleless drug delivery. Some reset mechanisms that are included as a part of the needleless injector include screw thread, hydraulic, lever arm, and the use of compressed gas. Other needleless injectors can be reset using a table top reset unit of a mechanical, electromechanical, or hydraulic nature, or can interface with a hard surface for reset purposes. Some carbon dioxide power supplies can be reset by interfacing with a household item such as a pencil or can be reset with a spring. The power supply of the present invention can interface with a screw thread, hydraulic, lever arm, compressed gas, a table top reset unit, or other reset mechanisms that are presented in most other needleless injector patents. Several other power supply devices include pyrotechnic devices, use of carbonic acid, and special gasses that can convert back and forth between a liquid and a gas in going from a compressed state to an unloaded or fired state.
Lindmayer disclosed in U.S. Pat. No. 4,623,332 a needleless injector that uses disk springs as a power supply to drive a piston forward and deliver liquid medicine from a medicine chamber and out of an orifice. A latch is used to hold the piston in a state of potential energy and a trigger is pressed to release the latch and discharge the medicine. A threaded mechanism is used to reset the coil spring for the next injection. This device is large and heavy due to the requirements placed on the springs to provide a large force in order to generate a high velocity stream out of the orifice. It is desired for the patient to be able to carry a needleless injector unobtrusively with himself such that drug injections can be made throughout the day if necessary. It is therefore desirable to have a more powerful power supply that is smaller and lighter. The power supply of the present invention could be adapted to work with the needleless injector of Lindmayer as well as with other needleless injectors as further discussed.
Several needleless injector devices disclose the use of one or more coil springs in the power supply to generate the energy needed to drive a liquid drug out of an orifice, including U.S. Pat. No. 4,722,728 by Dixon, U.S. Pat. No. 4,850,967 by Cosmai, U.S. Pat. No. 5,569,189 by Parsons, U.S. Pat. No. 3,805,783 by Ismach, U.S. Pat. No. 4,059,107 by Iriguchi, U.S. Pat. No. 4,400,171 by Dettbarn, U.S. Pat. No. 3,782,380 by Van Der Gaast, U.S. Pat. No. 5,501,666 by Spielberg, and U.S. Pat. No. 4,874,367 by Edwards. Problems with most coil springs when used as a power source include the characteristic that compressed springs quickly become weak as they begin to expand in length. In order to generate the forces needed to drive the liquid drug out through the orifice at a high velocity requires that a coil spring have a large spring constant and have a long length. As a result the needleless injector devices with coil springs tend to be larger and heavier than desired. These disclosures describe a variety of mechanism used to reset the coil spring power supply following activation to prepare it for a subsequent activation. The disclosures also use a variety of ampule types. Dixon (U.S. Pat. No. 4,722,728) and Cosmai (U.S. Pat. No. 4,850,967) disclose a screw thread mechanism to be used to reset the coil spring power supplies of their inventions; they each describe a reusable ampule that can be used with their needleless injectors.
Parsons (U.S. Pat. No. 5,569,189) describes a table top resetting fixture with a toggle clamp design that interfaces with the needleless injector of his disclosure to reset his coil spring powered needleless injector; he discloses an ampule that is reusable and looks very similar to a syringe. Ismach (U.S. Pat. No. 3,805,783) describes a coil spring powered power supply with a hydraulic reset built into the handle; he shows a removable medicament container or vile with a supply for containing the drug and a nonremovable muzzle or ampule. Iriguchi (U.S. Pat. No. 4,059,107) and Dettbarn (U.S. Pat. No. 4,400,171) each disclose a needleless injector with a compressed gas reset and a reusable ampule. Van Der Gaast (U.S. Pat. No. 3,782,380) and Spielberg (U.S. Pat. No. 5,501,666) each disclose the use of a mechanical lever to reset the coil spring power supplies in each of their devices. Van Der Gaast (U.S. Pat. No. 3,782,380) describes a detachable medicament cartridge and Spielberg (U.S. Pat. No. 5,501,666) describes an ampule or discharge chamber that is built into the needleless injector device. Edwards (U.S. Pat. No. 4,874,367) describes a reset mechanism that requires the needleless injector to be pushed against a hard surface for reset, this procedure can be dangerous; the ampule is a sterilized cartridge that is removable and can be reused. The power supply of the present invention can be used with any of the needleless injector devices disclosed in the patents listed above as well as the patents referenced by the above listed patents.
Another type of power supply is the gas spring wherein a compressed gas contained in a cylinder expands to drive a piston to supply the energy to drive the drug transcutaneously in a patient. This power supply offers the advantage of a smaller and light weight power supply that can store more potential energy per system size and weight than a mechanical spring power supply. One problem with this power supply system is that leakage of the compressed gas from the seal that separates the piston from the cylinder. This leads to eventual loss of function of the gas spring over time and with frequency of use. Additionally, gas spring costs can be higher than other power supply systems including mechanical springs and others.
One gas spring power supply for a needleless injector is disclosed in U.S. Pat. No. 5,599,302 by Lilley. In this design the air cylinder has a rod coming out of each end and as a result it has two sliding or active seals. This design is particularly prone to gas leakage due to the presence of two active seals. This device has a built in ampule that is removable for cleaning and has a threaded mechanism to reset the gas spring. Another needleless injector device that uses compressed gas as the power supply is described by Cohen in U.S. Pat. No. 4,421,508. Cohen describes a special ampule with a tube around it and is put under vacuum to hold the skin tight against the orifice when the needleless injector is fired or activated in order to get better penetration of the drug through the skin and into the underlying tissues. The same argument is made by Morrow (U.S. Pat. No. 4,790,824) as rationale for providing a space between the orifice and the skin. The device uses a vacuum to reset the power supply and has a reusable ampule.
Another power supply uses a carbon dioxide cylinder filled with carbon dioxide liquid as a supply of compressed carbon dioxide gas for driving a medicine or drug transcutaneously with a needleless injector. Problems with this type of power supply system include the difficulty with maintaining a constant pressure needed in order to control the dose that is delivered. In addition several disclosures show one or more sliding seals that can leak over time. Casey in U.S. Pat. No. 4,940,460, McKinnon in U.S. Pat. No. 5,503,627 and Morrow in U.S. Pat. No. 4,790,824 describe carbon dioxide compressed gas power supply systems. Casey (U.S. Pat. No. 4,940,460) and McKinnon (U.S. Pat. No. 5,503,627) disclose the use of a mechanical spring to reset the power supply and Morrow (U.S. Pat. No. 4,790,824) describes the use of a pencil to reset the carbon dioxide power supply. McKinnon (U.S. Pat. No. 5,503,627) describes a detachable reusable ampule with a lure fitting for filling and Morrow (U.S. Pat. No. 4,790,824) describes a reusable or a disposable ampule. Parsons discloses in U.S. Pat. No. 4,913,699 a carbon dioxide compressed gas power supply where carbon dioxide gas is contained in a glass container which is broken to release the gas. The ampule of this device is built into the needleless injector and the reset is hydraulically activated by the medicant being used. Lindmayer discloses in U.S. Pat. No. 4,342,310 a compressed gas power supply system that uses a special gas that converts from a liquid under pressure to a gas during the expansion or power portion of the cycle. This device has three active or sliding seals that are likely to leak over time and with frequency of use. A hydraulic pump is used to reset the power supply and it is designed to work with a reusable ampule. The power supply of the present invention can be used as a power supply in any of the needleless injectors mentioned above that use a compressed gas power supply that functions as a gas spring or in the needleless injectors that have carbon dioxide cylinders to supply compressed carbon dioxide gas as the power supply. The present power supply can interface with any of the reset mechanisms or can be compatible with any type of ampule described in the above referenced patents. The power supply of the present invention can also be used as a power supply in the patents that are referenced by the above mentioned patents.
Needleless injectors with varying types of power supplies are found to be compatible with a variety of ampule designs. Gasaway describes in U.S. Pat. No. 5,024,656 describes a carbon dioxide powered needleless injector that uses a reusable ampule that looks like a syringe. This device comes with an adapter for filling the syringe. McKinnon describes in U.S. Pat. No. 5,064,413 a carbon dioxide powered needleless injector that uses a built in but removable ampule. A disposable ampule design is described in U.S. Pat. No. 3,945,383 by Bennett; this ampule is designed to interface directly with a needleless injector. Parsons (U.S. Pat. No. 4,680,027) and Edwards (U.S. Pat. No. 5,073,165) each describe disposable ampules that are compatible with their own needleless injector designs. The power supply of the present invention can be compatible with needleless injector designs regardless of the type of ampule that is used with the system.
Doherty describes in U.S. Pat. No. 4,090,512 a remote mechanism that is used for resetting a needleless injector. Although the remote mechanism is described as being used with a coil spring powered injector, it could be used to reset almost any power supply. The power supply of the present invention could similarly be used with the Doherty device or with any of the reset devices that are a component of or that interface with the needleless injectors that have been referenced above.
Two additional patents are presented which discuss alternate power supply designs. In U.S. Pat. No. 4,089,334 by Schwebel a pyrotechnically powered needleless injector is presented. This type of power supply is dangerous, loud, and is not reproducible in generating a control force to drive a drug injection. Although the power supply is quite different from the power supplies presented in the prior art patents presented above, the Schwebel needleless injector device has a disposable ampule that is very similar to those that have been presented in the references above. Fejes discloses in U.S. Pat. No. 4,626,242 a needleless injector that is powered by carbonic acid gas. This needleless injector device has a mechanical spring to perform the reset of the power supply and it is designed for use with a reusable ampule. The reset mechanism and the ampule are very similar to those of other needleless injector devices presented in the prior art references listed above. The power supply of the present invention could be combined with components of either the Schwebel (U.S. Pat. No. 4,089,334) or the Fejes (U.S. Pat. No. 4,626,242) device to form a functional needleless injector device.